Pilkington Activ glass reduces the amount of sunlight passing through by only about 5%; the coating is very tough and would require real abrasion like a determined scrubbing with steel wool to take it off. It can greatly reduce the cost of cleaning large commercial buildings (or the windows in your house!). It also eliminates harsh cleaner residue from the environment.

SF fans may recall Window Willie, the window-washing invention from Robert Heinleins 1956 novel The Door Into Summer; the novel describes it as an "electrostatic device" that makes dirt disappear from any polished silica surface. I wonder if the coating would work on other kinds of surfaces?